1. Field of the Invention
This invention relates to a controller for a camera.
2. Related Background Art
An electric zoom camera capable of accomplishing so-called given magnification photography in which an object is photographed always at a predetermined size irrespective of the object distance by operating a given magnification setting button or the like has been proposed.
In the camera of this type, a plurality of magnification tables in which the object distance and the focal length are made to correspond to each other in advance are stored in CPU to change the focal length of the photographing lens in conformity with the object distance and make given magnification photography possible. By half depressing a release button after the given magnification photographing mode is set by the operation of the given magnification setting button, one of the tables is selected in the camera, and from that table, for example, a focal length corresponding to the object distance obtained by a distance measurement circuit is selected and set and the photographing lens is automatically driven to that focal length, and photographing is effected by the half depressing operation of the release button. In such magnification tables, the ratio of the object distance to the focal length, i.e., the photograph magnification is always made constant so that for example, the bust or the whole of a person is photographed always at the same size, and the photographer can also select the photograph magnification by the operation of an operating button or the like.
Also known is a camera in which a desired focal length is input in advance to the camera side by a manual operation and when the half depression operation of a release button is thereafter effected, a photographing lens is driven at a stroke to the input focal length.
However, in such a camera, when for example, a mode in which given magnification photography is effected is set, the camera side automatically sets the focal length of the photographing lens and effects zooming, and therefore it is sometimes the case that the composition is not satisfactory to the photographer, and this leads to the problem that the usability of the camera is poor.
Also known is a camera in which, as disclosed, for example, in Japanese Patent publication No. 51-27577, the focal length of a photographing lens such as a zoom lens is automatically adjusted so that a predetermined photograph magnification is always provided even if the photographing distance varies for the same object, thereby accomplishing photographing.
Now, in a photographing lens capable of photographing at a plurality of focal lengths, such as a zoom lens, the full open aperture stop value differs with a variation in the focal length and therefore, for example, where the zoom lens is driven to the telephoto side, in spite of the fact that before the driving, it is not necessary to cause a flash device to emit light for the same composition, the full open aperture stop value becomes greater (e.g., F2.fwdarw.F5.6) after the driving and the necessity of light emission sometimes arises. Hereinafter, the light emission by the flash device will be referred to as flash light emission.
In the conventional camera, however, after the zoom lens is driven to a predetermined focal length, calculation of an exposure value is effected by the use of a full open aperture stop value conforming to that focal length. Accordingly, whether flash light emission is necessary after the driving of the photographing lens can be known, and when flash light emission is necessary, charging is started at that point of time. Therefore, photographing cannot be accomplished due to uncompleted charging in spite of the lens having been set to the predetermined focal length, and this may give displeasure to the photographer.